Air Core, Toroid Coil Calculator Programs

The coil has an inductance (expressed in Henry and submultiples – “L”), a ballast to the passage of alternating current (expressed in Ohms – “X”), a resistance to the passage of direct current (“R” – in Ohms) , a factor of merit.

L ‘inductance is the ability to store electrical energy in an electromagnetic field. The ballast is an electrical resistance element that offers to the passage of an alternating current having a certain frequency. The factor of merit (or quality) expressed with the letter Q is the ratio of the reactance (inductive in this case) and the sum of all the losses associated with the decrease in energy in transit

Air Core Calculator Program

The toroidal cores (Amidon is one of the major manufacturers) have extensive application in radio frequency circuits and power supplies.

The magnetic materials used for the construction of the toroidal cores are many but the two main ones are: iron powder (iron powder) and the ferrite. The salient features of these nuclei are: the size, the permeability (μ), the frequency range and maximum power.

The permeability is the ratio of flux density in the material (B) and the flux density in the air (H): in other words is the measure of the relative ease with which a magnetic flux is established, the symbol that represents it is the Greek letter μ (μi = micro index). With increasing H, B tends to saturate as there is a limit value of induction when all the magnetic dipoles align with the field of material required. In general, the higher the permeability, the lower the working frequency recommended.

Toroid Coil Calculator Program

SINGLE LAYER COILS

The coil has an inductance (expressed in Henry and submultiples – “L”), a reactance to the passage of alternating current (expressed in Ohm – “X”), a resistance to the passage of direct current (“R” – in Ohm) , a certain merit factor.

Inductance is the ability to store electrical energy in an electromagnetic field.
Reactance is the electrical resistance that an element offers to the passage of an alternating current of a certain frequency.
The merit (or quality) factor expressed with the letter Q is the ratio between the reactance (inductive in this case) and the sum of all the losses associated with the decrease in energy in transit:

COILS WITH AMIDON TOROIDS

Toroidal cores (Amidon is one of the main manufacturers) find wide application in radio frequency circuits and power supplies.

The reasons that push a designer to prefer these cores to others are:

• self-shielding behavior, as the flux remains confined within the magnetic core
• the precision and repetitiveness of the inductance values and the quality factor
• the absolute ease of positioning during assembly
• high Q even in broadband circuits

There are many magnetic materials used for the construction of toroidal cores but the two main ones are: iron powder and ferrite.

The salient characteristics of these nuclei are: the dimensions, the permeability (µ), the frequency range and the maximum applicable power.

Permeability is the ratio between flux density in the material (B) and flux density in air (H): in simple terms it is the measure of the relative ease with which a magnetic flux is established, the symbol that represents it is the Greek letter µ ( µi = micro index ). As H increases, B tends to saturate as there is a limit induction value when all the magnetic dipoles of the material align with the imposed field. Generally the higher the permeability, the lower the recommended working frequency.

The iron powder toroid (T series) is able to tolerate high powers (the T300 for example supports 800 Watt RF) and is subject to minor variations in permeability therefore excellent for oscillators, an example is the yellow core 6 which is very stable as long as the coils are glued to the core to avoid vibrations and movements of the wire with consequent frequency drifts.
The ferrite core (FT series) has a greater permeability so fewer turns are needed for the same inductance (ideal for RF chokes and broadband transformers) however it is less stable as the temperature varies.

It must be said that if the specified flux density is exceeded (if the core is saturated) the toroid overheats and its permeability changes; Iron powder cores do not get damaged and return to their initial characteristics, while ferrite cores can be permanently damaged.

As regards the construction of the coils, the power of the signal in transit must be considered; with modest signals, enamelled copper with a section of 0.18 to 1 mm is fine; if the power is high, it is necessary to use rigid wire covered in PVC (like that used in electrical systems) with a large diameter, even 1.5 or 2 mm (the advice of “some” is to wrap the core with insulating tape before building I have never shared the coil itself… especially if you work on VHF).. If the power involved is really high (e.g. in baluns or ununs) and there are overheating problems, the best thing is to glue with epoxy resin two cores together so as to use them as a single toroid.

The winding must occupy approximately 330 of the 360 degrees available; no further to avoid parasitic capacitances, no less to fall within the parameters of the sizing formulas.

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